[goffice] dtoa: improve long double handling.

[Morten Welinder <mortenw src gnome org>]

commit 37ad61f0e1649c27d09310d05cef6310f1c500e7
Author: Morten Welinder <terra gnome org>
Date:   Wed Apr 9 10:00:18 2014 -0400

    dtoa: improve long double handling.

 ChangeLog              |    4 ++++
 goffice/math/go-dtoa.c |   19 ++++++++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index ccf2cb1..2e5025b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2014-04-09  Morten Welinder  <terra gnome org>
+
+       * goffice/math/go-dtoa.c (go_dtoa): Improve long-double handling.
+
 2014-04-07  Morten Welinder  <terra gnome org>
 
        * goffice/math/go-dtoa.c (fmt_fp): Three fixes from musl.  (One we
diff --git a/goffice/math/go-dtoa.c b/goffice/math/go-dtoa.c
index 457308d..96c352e 100644
--- a/goffice/math/go-dtoa.c
+++ b/goffice/math/go-dtoa.c
@@ -390,11 +390,10 @@ static int fmt_fp(FAKE_FILE *f, long double y, int w, int p, int fl, int t)
 /* musl code ends here */
 
 static void
-parse_fmt (const char *fmt, va_list args,
+parse_fmt (const char *fmt, va_list args, gboolean *is_long,
           int *w, int *p, int *fl, int *t, long double *d)
 {
-       gboolean is_long = FALSE;
-
+       *is_long = FALSE;
        *w = 1;
        *p = -1;
        *fl = 0;
@@ -430,7 +429,7 @@ parse_fmt (const char *fmt, va_list args,
        }
 
        if (*fmt == 'L') {
-               is_long = TRUE;
+               *is_long = TRUE;
                fmt++;
        }
 
@@ -438,7 +437,7 @@ parse_fmt (const char *fmt, va_list args,
                return;
        *t = *fmt;
 
-       if (is_long)
+       if (*is_long)
                *d = va_arg (args, long double);
        else
                *d = va_arg (args, double);
@@ -452,13 +451,19 @@ go_dtoa (GString *dst, const char *fmt, ...)
        int w, p, fl, t;
        va_list args;
        long double d;
+       gboolean is_long;
        gboolean debug = FALSE;
 
        va_start (args, fmt);
-       parse_fmt (fmt, args, &w, &p, &fl, &t, &d);
+       parse_fmt (fmt, args, &is_long, &w, &p, &fl, &t, &d);
        va_end (args);
 
-       if (fl & FLAG_SHORTEST) p = 17;
+       /*
+        * FLAG_SHORTEST isn't fully implemented yet.  For now we just
+        * ensure a roundtrip.
+        */
+       if (fl & FLAG_SHORTEST) p = is_long ? 20 : 17;
+
        if (debug) g_printerr ("%Lg [%s] t=%c  p=%d\n", d, fmt, t, p);
        fmt_fp (dst, d, w, p, fl, t);
        if (debug) g_printerr ("  --> %s\n", dst->str);